US 2005/0 045 618 A1 describes such a device. The individual heating elements each extend over a full circle. Devices with heating elements that meander in a plane are shown in US 2004/0 149 227 A1, US 2010/0 162 956 A1 and U.S. Pat. No. 5,063,031.
US 2006/0 185 595 A1 describes linear heating elements that are electrically parallel connected, wherein the heating elements and contact plates allocated thereto run in a shared plane.
A U-shaped heating element is described in DE 75 18 153 U.
Devices for heating the susceptors of CVD reactors are also known from DE 10 2009 043 960 A1, DE 10 2007 009 145 A1, DE 103 29 107 A1, DE 10 2005 056 536 A1, DE 10 2006 018 515 A1 or DE 10 2007 027 704 A1.
In a known heating element, heat is generated by a current flowing through a resistance heating unit. The resistance heating unit has a first and a second end, where first and second terminal contacts are located. The terminal contacts run parallel to each other, but vary in length. The first, shorter terminal contact is connected with a first contact plate consisting of an electrically conductive material. A second electrical contact plate runs in a parallel plane to the first contact plate, but at a greater distance from the resistance heating unit. The two electrical contact plates extend one over the other, as it were. The longer second terminal contacts are passed through openings in the first contact plate, and are connected with the second contact plate. The openings through which the second terminal contacts pass are larger than the diameter of the second terminal contacts, thus leaving a distance between the edge of the opening and the second terminal contacts. This free space isolates the second terminal contact from the first contact plate. Significant thermal stresses arise while heating or cooling the resistance heating units of the heating elements in prior art. These mechanical stresses can lead to an irreversible deformation of the contact plates. As a result, short circuit bars form between the second terminal contacts and the openings of the electrically conductive first contact plate after prolonged use, and in particular after repeated heating and cooling. As a rule, this then results in the destruction of the entire heating element. The metal evaporating in the process can also contaminate the processing chamber of the CVD reactor in which the device is used.